1. Not only are amino acids required for the synthesis of proteins, but some amino acids (particularly the branched chain amino acid leucine) can function as signaling molecules. Of particular importance to nutrition is a protein complex known as mammalian target of rapamycin (mTORC1) that is activated in response to leucine. Using your advanced research skills, discuss the mechanisms through which leucine signals an increase in protein synthesis through the activation of mTORC1. You may find it useful to focus on ribosomal protein S6 kinase (S6K1) and eukaryotic initiation factor 4E binding protein (eIF4E-BP).
2. Amino acid deprivation leads to the inhibition of mTOR signaling and stimulates protein degradation through autophagy (lysosomal proteolysis). In addition to autophagy, amino acid deprivation also activates the ubiquitin proteasome system. Ubiquitin (Ub) is a small peptide that is attached to some proteins so that they are directed to the proteasome. Illustrate the role(s) of Ub-activating enzyme (E1), Ub-conjugating enzymes (E2), and Ub-ligases (E3) as they relate to protein ubiquitylation.
3. Explain the role of the 26S proteasome as it relates to proteasomal degradation. Also discuss requirements, if any, for energy in this process.
1. Not only are amino acids required for the synthesis of proteins, but some amino acids (particularly the branched chain amino acid leucine) can function as signaling molecules. Of particular importance to nutrition is a protein complex known as mammalian target of rapamycin (mTORC1) that is activated in response to leucine. Using your advanced research skills, discuss the mechanisms through which leucine signals an increase in protein synthesis through the activation of mTORC1. You may find it useful to focus on ribosomal protein S6 kinase (S6K1) and eukaryotic initiation factor 4E binding protein (eIF4E-BP).
2. Amino acid deprivation leads to the inhibition of mTOR signaling and stimulates protein degradation through autophagy (lysosomal proteolysis). In addition to autophagy, amino acid deprivation also activates the ubiquitin proteasome system. Ubiquitin (Ub) is a small peptide that is attached to some proteins so that they are directed to the proteasome. Illustrate the role(s) of Ub-activating enzyme (E1), Ub-conjugating enzymes (E2), and Ub-ligases (E3) as they relate to protein ubiquitylation.
3. Explain the role of the 26S proteasome as it relates to proteasomal degradation. Also discuss requirements, if any, for energy in this process.
